Dryer for photoprints



1967 R. E. ZIMMER DRYER FOR PHOTOPRINTS Filed Jun 22, 1966 5Sheets-5heet l A'r'rYS.

3 Sheets-Sheet 2 Dec. 5, 1967 Filed June 22, 1966 5& gTHEP/WOSTAT HIGHL/M/T THERMOS TAT) MA MI SWITCH llii lNveN'rcP. ROBERT 5.2mm:

,1445% MW, v jw,

, ATTVS.

Dec. 5, 1967 R ZMMER 3,355,815

DRYER FOR PHOTOPRIN'I'S Filed June 22, 196g QQN 5 Sheets-Sheet 5INVENTOR oeERT E. ZIMMER Arrvs.

United States Patent 3,355,815 DRYER FOR PHOTOPRINTS Robert E. Zimmer,Niles, Ill., assignor to American Photocopy Equipment Company, Evanston,Ill., a corporation of Illinois Filed June 22, 1966, Ser. No. 559,607 9Claims. (Cl. 34-48) ABSTRACT OF THE DISCLOSURE A dryer for photoprintsor the like employing a drum and a fabric belt, distinguished by use ofmain and auxiliary heaters with controlled application of radiant andconvected heat.

It is an object of the present invention to provide a dryer forphotoprints which is highly efficient, acting simultaneously on the backand front sides of the prints and which is capable of operating at ahigh rate on a production basis. It is a related object to provide adryer for photoprints capable of continuous operation, which is easilyadjusted to the conditions of use, and in which the operation isautomatically controlled for consistent operation over long periods oftime. In this connection it is an object to provide a print dryer whichavoids any possibility of scorching the prints, or the belt whichcarries them, either as a result of overshooting of the temperature onstart-up or as a result of temperature buildup in the machine whencontinuously operated over long periods of time.

It is another object of the present invention to provide a print dryerwhich is capable of handling all types and sizes of prints normallyproduced in a photographic workroom, either black and white or color,and which tolerates a wide range of 'water content. It is a morespecific object to provide a print dryer which not only removes themoisture absorbed in the prints but which presses out excess water asthe prints are fed into the machine, continuously disposing of theexcess without care or attention on the part of the operator.

It is yet another object of the present invention to provide a printdryer which is capable of operating at a high commercial rate but whichis nevertheless highly compact, semi-portable, and more economical bothin first cost and in operation, than commercial print dryers inconventional use.

Other objects and advantages of the invention will become apparent uponreading the attached detailed description and upon reference to thedrawings in which:

FIGURE 1 is a perspective view of a print dryer constructed inaccordance with the invention;

FIGURE 2 is a vertical section of the machine taken along the line 2-2in FIGURE 3;

FIGURE 3 is a vertical section taken through the axis of the machinealong the line 33 in FIGURE 2;

FIGURE 4 is a fragmentary section taken through the drum along the line4-4 in FIGURE 3;

FIGURE 5 is a fragmentary view looking along the line 55 in FIGURE 4;and

FIGURE 6 is a wiring diagram.

While the invention has been described in connection with a preferredembodiment, it will be understood that I do not intend to be limited tothe embodiment shown but intend to cover the various alternative andequivalent constructions included within the spirit and scope of theappended claims.

Turning now to the drawings, the print dryer 10 has a frame including apair of side members 11, 12 joined by cross members 13, a rear panel 14and a top panel or grill 15. The side frame members 11, 12 are fittedwith cover plates 16, 17, respectively, which are removable to provideaccess to spaces 18, 19 which accommodate wiring and certain accessoryparts as will be discussed.

Largely filling the central space between the side members is a hollowdrum 20 of thermally conductive material enclosed by ends 21, 22 andhaving bearings 23, 24 mounted on a hollow stationary shaft 25. Theshaft may be prevented from rotating by cutting, in one or both ends, atransverse keyway 26 engaged by a key plate 27. The walls of the drummay, for example, be formed of stainless steel, chromium plated andhighly polished to impart gloss to a so-called glossy print.

For the purpose of holding the prints with face to the drum as they aredried, a web or belt 30 is provided having a drum engaging portion 31which extends most of the way around the drum, and a return portion 32,leaving the front of the drum freely accessible for discharge asindicated at 33. The belt 30 is preferably of woven fabric having awidth extending substantially the full length of the drum and seamed sothat it is endless. The return portion of the belt in the machine isguided by a set of transversely extending shafts to define a rearchamber 34 at the back of the drum. Whether a shaft is in the form of apolished stationary bar or in the form of a journalled roller is largelya matter of choice, a bar being less expensive. Thus the belt is passedabout a first bar 35 at the front of the machine, upwardly about a bar36, and then rearwardly along a horizontal run 37 to a drive roller 40.The drive roller is rotated by a drive pulley 41 and driven pulley 42interconnected by a belt 43. The drive pulley is connected through agear train (not shown) to a drive motor 44 which may, for example, be ofthe shaded pole type having a speed control unit 45.

To provide adequate wrap-around on the driven roller 40, the belt 30passes around a shaft 46, a take-up roller 47 and shaft 48 from whichthe belt passes downwardly along a vertical run 49 along the back of themachine. The belt then makes a right-angle turn 50 and proceeds along ahorizontal run 51 forwardly to an apron roller 53. At the rear end ofthe apron roller (FIG. 2) is a hub 54 having an adjusting screw 55 toadjust tracking. The apron roller is supported in an apron tray 56having alined pivots 57. Thus the apron roller, in its forwardlyextended position at the front of the machine, defines a run of belt 58which may be referred to as the apron on which the prints are placed,for example, a print 59, face up, for feeding into the machine.

For defining a hip between the belt and the surface of the drum and forapplying pressure resiliently to squeeze excess water out of the prints,a squeegee roller 60, of rubber or the like, is provided. Such roller ismounted on a pair of arms 61, only one of which is shown, pivoted to theside members indicated at 62 and biased upwardly by individual biasingsprings 63. Each spring has an adjustable anchor 64 for setting theroller pressure. Throwoff is achieved by cams 65 having a shaft 66 andthrowoff arm 67. The pressure applied by the squeegee roller issufficient to press out the excess moisture which overflows onto thebelt and which is immediately absorbed by the belt fabric. Any moisturewhich might drip through the apron is caught by the lower pass of thebelt immediately below the apron. After passing through the nip, theprints are conducted in face contact with the moving drum until thedischarge region 33 at the front of the drum is reached, at which pointthe prints peel off falling into a receiving tray 70 extending the widthof the drum and spaced above the apron. The receiving tray is: pivotedat 71 to the side members and is connected to the apron tray by a pairof links 72, only one of which is shown, having pivots '73, 74. For thepurpose of limiting the downward swing of the apron tray and receivingtray, a pair of drop links 75 are provided which are connected at theirlower ends to the pivot 73 and which are formed with hooks 76 at theirupper ends for hooking onto the pivots 71. Where the dryer is mounted onan extensive supporting surface, the supported position of the aprontray is defined by one or more pads 77 along the edge of the tray.

For the purpose of heating the drum, a heating assembly 80 is provided(see FIGS. 4 and in which the heater 81 is in the form of parallelconductors such as nichrome wire or the like supported in a reflector 82adjacent the inside bottom surface of the drum. The reflector issuspended on hangers S3, 84 from the stationary shaft 25. As indicatedin FIG. 4, the reflector is partially enclosed at the left-hand orupstream end by a downwardly turned lip 85 While at the opposite end anupturned lip 86 is provided for escape of the heated air along themoving inner surface of the drum in the direction of the arrow 87. Theheater leads 88, 89 are brought out through the hollow shaft 25. It willbe apparent, then that as the drum rotates the inner surface issubjected to both radiant and convected heat, with all portions of thedrum being acted upon uniformly as it revolves.

In accordance with the present invention, a second heater, serving as anauxiliary source of heat, is provided at the rear of the drum, in thechamber 34 formed by the return pass of the fabric belt, with anassociated, vertically extended guide surface, or plate, spaced from theback of the drum defining a chimney for vertical convection of theheated air closely adjacent the rear surface of the drum and with atemperature controlling thermostat spaced close to the drum in the pathof the flow. Referring to the drawings and particularly to FIG, 2, Iprovide in the chamber 34 at the rear of the drum a heating element ashaving supply lines 91,92. Such heater is preferably in the form of aresistive plate having terminals at its edges and commercially availableunder the name Cellotherm from Chemelex, Incorporated, of Danbury, Conn.For guiding the upwardly convected air with chimney action about thesurface of the drum a guide plate 95 is provided which bridges the spacebetween the two side members 11, 12 and which is bent at the center tofollow the contour of the drum. Such plate is preferably formed ofaluminum or other good conductor so that, in addition to acting asguides for the air stream, they also serve, particularly the plate 95,to distribute over a broad area the heat generated in the heatingelement 90. It will be apparent therefore, that the heat from theelement 90 is transferred in three possible modes: conduction into theplate 95, direct radiation from the surface of the plate, andconvection, augmenting the convection caused by the heated drum itself.Thus the air entering at 96 through the bottom of the housing, boththrough and around the edges of the belt passes along the plate to beginits upward ascent. Between the two sources of heat, the air is heated,taking on the moisture given off by the prints and rises along the pathof the arrows 97, being vented at the top through the horizontal run 37of the fabric belt. As the heated air passes through the pores of thefabric it tends to carry otf what remains of the moisture from theprints including that due to the action of the squeegee roller 60.Further drying takes place along the vertical run 49 and horizontal run51. Thus by the time that any portion of the belt finally returns to theloading apron, it is substantially dry and ready to absorb moisture fromthe prints including that which is pressed out at the squeegee roller.For the purpose of thermostatically controlling the heating elementwithin the drum, there is a thermostat positioned at the upper end ofthe chimney air stream and in proximity to the drum surface. Thethermostat, indicated at 100, is preferably of the type, well known inthe art, having a responsive bulb and bellows operating switch contacts101 and having adjusting knob 102.

In accordance with one of the important features of the presentinvention, a high limit thermostat is provided Within the drum, andpreferably in the space above the [I heating element for insuring thatthe temperature in the drum does not exceed a safe value either duringstart-up or under any running conditions. Thus I provide a thermo stat110 (see FIGS. 4 and 5) having a frame 111 in which is mounted atemperature responsive element in the form of a bimetal 112 connected bya plunger 113 to a switch contact assembly 114. The contacts areconnected in series with the contacts 101 of the main thermostat asshown in FIG. 6 so that the heating element is effectively turned off inthe event the temperature within the drum tends to exceed a certain,safe value and even then the main thermostat may be calling for heat.This function is particuarly important when the unit is first turned on,at which time the temperature tends to rise Within the drum with onlylimited initial effect upon the main thermostat 1%. In a practical casethe high limit thermostat may be set to cut off flow of current at, say,260 F. whereas the main thermostat may be set within a range of, say,180- 200 F. As a result of using the high limit thermostat, a largewattage element may be used within the drum for rapid response and heavyload carrying ability while nevertheless insuring against the creationof a temporary high temperature during the interval immediately following turn-on or following a sudden change in the setting of the controlknob or a sudden change in loading. It is found that with the presentset-up prints may be fed into the dryer Within a short time after thedevice is turned on.

without risk of overheating or scorching the prints or the fabric belton which they are carried. If desired the wattage of the heater in thedrum may be in excess 0 800 watts and the wattage of the auxiliaryheater may be some fraction of this. Since the auxiliary heater is oflesser wattage and coupled more loosely to the prints, serving toaugment the main heater, the auxiliary heater is preferably constantlyenergized.

For the sake of easy understanding the circuit diagram shown in FIG. 6has been considerably simplified, having a switch 120 in series with theregular A-C supply line. In use, the apron tray 56 and receiving tray76' are pulled down from the vertical nested position to the extendedposition shown in FIGS. 1 and 2. The switch 120 is turned on and thespeed control 45 and thermostat at 110 serv ing to keep the peaktemperature within the drum within safe limits until the main thermostatoutside the drum can take over its automatic control function. Printsare placed face-up upon the apron and pass around the drum as discussed.In the event that a print has not com pletely dried during a singlecircuit, it simply remains on the drum for a second pass. The speed andtemperature are so adjusted that under a given set of conditions theprints are dry by the time that they are circulated around to the space33 at the front of the machine, peeling off automatically and droppinginto the receiving tray 70. It has been found that a machine of theconstruction described above is capable of continuous operation on aproduction basis, replacing in many instances the larger and heaviermachines which have been previously thought to be necessary. Since thepresent machine is inherently inexpensive and compact, it may beemployed, not only on production work, but in ,a photo laboratory or thelike where the machine may be turned on and off repeatedly during thecourse of a days work.

As the drum rotates the air which has been heated by the heating elementwithin the reflector 82 passes upwardly and rearwardly along the insidesurface of the drum as indicated by the arrow 87 in FIG. 4, losing heatto the drum wall in the process. Such air is transferred to the top halfof the drum where it alfects the thermostat and, upon beingprogressively cooled, flows downwardly along the front side of the drumand into the space below the reflector to replenish the air under thereflector, with the cycle being endlessly repeated. By reason of thecirculation, quick response of the thermostat 110 is. assured to.prevent any uncontrolled peaks of temperature regardless of the load orregardless of the setting of the controls.

In the claims the term guide surface refers to any surface spacedadjacent the back side of the drums and the term lower portion refers toa position sufficiently low as to create an upwardly rising current ofheated air along the backside of the drum.

I claim as my invention:

1. In a dryer for photoprints or the like, the combination comprising, aframe, a hollow drum of thermally conductive material rotatable therein,an endless fabric belt of porous construction having a drum engagingportion which extends about the major portion of the drum peripherywhile leaving the face of the drum accessible and a return portiondefining a rear chamber, a set of shafts for guiding the return portionof the belt including a shaft arranged forwardly of the drum defining anapron, a motor for driving the belt, a first electric heating element inthe drum for heating the face of the photoprints thereon, a secondelectric heating element in the lower portion of said chamber and spacedfrom the rear of the drum for simultaneous heating of the backside ofthe photoprints, thermostatic means for controlling the temperature ofat least one of the heating elements, the second heating element havingan associated vertically extending guide surface spaced from the back ofthe drum to define a chimney for the vertical flow of heated air closelyadjacent the rear surface of the drum.

2. The combination as claimed in claim 1 in which the second heatingelement has an associated vertically extending guide plate bent toconform to the back of the drum and extending vertically to a positionadjacent the return portion of the belt to define a chimney for thevertical flow of heated air along the rear surface of the drum forpassage of at least a portion of the heated air upwardly through thepores in the return portion of the belt for drying the belt prior to itsreturn to the drum.

3. In a dryer for photoprints or the like, the combination comprising, aframe, a hollow drum of thermally conductive material rotatable therein,an endless fabric belt having a drum engaging portion which extendsabout the major portion of the drum periphery while leaving the face ofthe drum accessible and a return portion defining a rear chamber, a setof shafts for guiding the return portion of the belt including a shaftarranged forwardly of the drum defining an apron, a motor for drivingthe belt, a first electric heating element in the drum for heating theface of the photoprints thereon, a second electric heating element insaid chamber and spaced from the rear of the drum for simultaneousheating of the backside of the photoprints, thermostatic means forcontrolling the temperature of at least one of the heating elements, thesecond heating element including a plate of heat conducting metalextending vertically and spaced from the back of the drum for conductivedistribution of the heat from the element as well as for defining achimney for the vertical flow of heated air along the rear surface ofthe drum.

4. In a dryer for photoprints or the like, the combination comprising, aframe, a hollow drum of thermally conductive material rotatable therein,an endless fabric belt having a drum engaging portion which extendsabout the major portion of the drum periphery while leaving the face ofthe drum accessible and a return portion defining a rear chamber, a setof shafts for guiding the return portion of the belt including a shaftarranged forwardly of the drum defining an apron, a motor for drivingthe belt, a first electric heating element in the drum for heating theface of the photoprints thereon, a second electric heating element insaid chamber and spaced from the rear of the drum for simultaneousheating of the backside of the photoprints, thermostatic means forcontrolling the temperature of at least one of the heating elements, thesecond heating element having an associated vertically extending surfacespaced from the back of the drum for defining a chimney for the verticalflow of heated air along the rear surface of the drum and in which thethermostatic means is located in the upper portion of the path of flowof the heated ,air in the chimney.

5. In a dryer for photoprints or the like the combination comprising aframe, a hollow enclosed drum of thermally conductive material rotatabletherein, an endless fa-bric belt having a drum-engaging portionextending about the drum periphery while leaving the face of the drumaccessible and a return portion defining a rear chamber, a set of shaftsfor guiding the return portion of the belt, a motor for driving the beltand engaged drum, a first electric heating element in the drum forheating the drum surface by radiation and convection, a second electricheating element in said chamber closely spaced from the rear of the drumfor heating the backside of the prints by radiation and for augmentingthe flow of a convection current of heated air along the back of thedrum, a thermostat in the convection current of air controllinglycoupled to the first heating element, and a high limit thermostat in theupper portion of the drum overridingly coupled to the first heatingelement for limiting the temperature in the drum to a value safely belowthe scorching temperature.

6. The combination as claimed in claim 5 in which the first heatingelement is in the form of radiant conductors at the bottom of the drumhaving an associated reflector vented to permit escape of heated airalong the inside surface of the drum and in which the first heatingelement has an output when energized which is substantially greater thanthe output of the second heating element.

-7. In a dryer for photoprints or thelike the combination comprising aframe, a hollow enclosed drum of thermally conductive material rotatabletherein, an endless fabric belt having a drum-engaging portion extendingabout the major portion of the drum periphery while leaving the face ofthe drum accessible and a return portion defining a rear chamber, a setof shafts for guiding the return portion of the belt, a motor fordriving the belt and engaged drum, an electric heating element in thelower portion of the drum for heating the drum surface by radiation andconvection, means in said chamber for producing a rising current ofheated air along the back of the drum to carry away the moisture fromthe prints, a main thermostat outside of the drum but in the airadjacent thereto and connected to the heating elernent for correctivelycontrolling the drum temperature, and a high limit thermostat in theupper portion of the drum having contacts effectively connected inseries with the main thermostat for limiting the temperature in thedrum.

8. In a dryer for photoprints or the like combination comprising aframe, a hollow enclosed drum of thermally conductive material rotatabletherein, an endless fabric belt having a drum-engaging portion extendingabout the drum periphery while leaving the face of the drum accessibleand a return portion defining a rear chamber, a set of shafts forguiding the return portion of the belt, a motor for driving the belt andengaged drum, a first electric heating element in the drum for heatingthe drum surface by radiation and convection, a second electric heatingelement in said chamber closely spaced from the rear of the drum andhaving a heating capacity less than that of the first element forheating the back-side of the prints by radiation and for augmenting theflow of a convection current of heated air along the back of the drum,and a thermostat in the upper portion of the drum' controllingly coupledto the first heating element for limiting the temperature in the drum.

9. In a dryer for photoprints or the like the combination comprising aframe, a hollow enclosed drum of thermally conductive material rotatabletherein, an endless fabric belt having a drum-engaging portion extendingabout the major portion of the drum periphery while leaving the face ofthe drum accessible and a return portion defining a rear chamber, a setof shafts for guiding the return portion of the belt, a motor fordriving the belt and engaged drum, a radiant electric heating elementclosely adjacent to the lower portion of the drum for heating the drumsurface, a reflector overlying the heating element and having lipsextending along the length thereof, the lips being dimensioned tofacilitate escape of heated air in the direction of movement of thebottom surface of the drum for flow of air upwardly along the back ofthe drum in a circular path and downwardly along the front surface toreplenish the air under the reflector, means in said chamber fordirecting a rising current of heated air along the back of the drum tocarry away the moisture from the prints, and a thermostat in the upperportion of the drum having contacts connected in series with the heatingelement for limiting the temperature in the drum.

References Cited UNITED STATES PATENTS 1,593,161 7/1926 Denham et a134-234 X 2,184,663 12/1939 Dye 34-123 X 2,526,318 10/1950 Battin 34-116X 2,896,336 7/1959 Shournatoff 34-116 X 3,002,290 10/1961 Abdoo 34-1233,157,390 11/1964 Douglas 34-48 JAMES W. \VESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, JR., Examiner.

A. D. HERRMANN, Assistant Examiner.

1. IN A DRYER FOR PHOTOPRINTS OR THE LIKE, THE COMBINATION COMPRISING, AFRAME, A HOLLOW DRUM OF THERMALLY CONDUCTIVE MATERIAL ROTATABLE THEREIN,AN ENDLESS FABRIC BELT OF POROUS CONSTRUCTION HAVING A DRUM ENGAGINGPORTION WHICH EXTENDS ABOUT THE MAJOR PORTION OF THE DRUM PERIPHERYWHILE LEAVING THE FACE OF THE DRUM ACCESSIBLE AND A RETURN PORTIONDEFINING A REAR CHAMBER, A SET OF SHAFTS FOR GUIDING THE RETURN PORTIONOF THE BELT INCLUDING A SHAFT ARRANGED FORWARDLY OF THE DRUM DEFINING ANAPRON, A MOTOR FOR DRIVING THE BELT, A FIRST ELECTRIC HEATING ELEMENT INTHE DRUM FOR HEATING THE FACE OF THE PHOTOPRINTS